/// <summary>
 ///     Invokes the <see cref="Navigating" /> event.
 /// </summary>
 protected virtual bool RaiseNavigating(NavigatingCancelEventArgs args)
 {
     EventHandler<INavigationService, NavigatingCancelEventArgsBase> handler = Navigating;
     if (handler != null)
     {
         handler(this, args);
         return !args.Cancel;
     }
     return true;
 }
 protected virtual bool RaiseNavigating(NavigatingCancelEventArgs args)
 {
     var handler = Navigating;
     if (handler != null)
     {
         handler(this, args);
         return !args.Cancel;
     }
     return true;
 }
 static NavigatingCancelEventArgs()
 {
     NonCancelableEventArgs = new NavigatingCancelEventArgs();
 }